Alternating current generator with improved fans system

ABSTRACT

In an alternating current generator and fans thereof in accordance with the invention, the cooling efficiency of the alternating current is improved by fans fixed to a rotor. When the fans are formed during a press working operation, the blades are formed directly from the fans by cut-raising the fans toward a bracket side to form blades and simultaneously cut-raising protruding potions toward a rotor side to form protrusions. This design allows for both improvement in cooling efficiency of the alternating current generator and ease of manufacture of the fans.

This is a continuation of Application Ser. No. 08/650,308 filed May 20,1996, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an alternating current generator withan improved fan system, and more particularly, to an alternating currentgenerator in which a rotor is provided with fans for producing coolingair.

The instant application claims priority from Japanese Patent ApplicationNo. HEI 7-287289, filed Nov. 6, 1995, which is incorporated herein byreference for all purposes.

2. Description of Related Art

U.S. Pat. No. 4,492,885 discloses a conventional alternating currentgenerator in which a rotor is provided with fans to produce cooling airfor cooling the alternating current generator itself.

One of the conventional alternating current generators is hereinafterdiscussed.

FIG. 15 is a sectional view showing the conventional alternating currentgenerator for a car. FIG. 16 is a perspective view showing a rotor ofthe generator. FIG. 17 is a partial perspective view showing a fan(ventilating portion) 14 which is attached to the rotor.

As shown, the alternator includes a rotor 1, a rotary shaft 11 driven bya driving force transmitted from an internal combustion engine of a car(not shown) by way of a belt (not shown), a pair of Rondel-type fieldcores 12, and a field winding 13. The alternator further includes astator 2 having a stator core 21 and a stator winding 22 which faces therotor 1 at a predetermined distance therefrom. A front bracket 3 and arear bracket 4, rotatably support the rotor 1 through bearings 31, 41and securely hold the stator 2 therebetween. Fans 14, 15 are fixed tothe Rondel-type field core 12. Blades 14 a, 15 a are formed bycut-raising the fans 14, 15.

The Rondel-type field cores 12 are formed into a Rondel-shape as shownin FIG. 15 by the steps of forming a low carbon steel or the like into astar shape by forging, etc. and bend-raising a nail portion 12 bprojecting from a core portion 12 a.

With regard to the operation of the conventional alternating currentgenerator of the above-construction, when the rotor 1 is rotated by anexternal driving force, a magnetic field generated by the field winding13 surrounds the Rondel-type field cores 12, and the magnetic fieldpasses through the stator winding 22 in conformity with the rotation ofthe rotor 1, whereby a current is generated on the stator winding 22 andpower is generated through a rectifier 5.

Furthermore, when the rotor 1 is rotated, the fans 14 and 15 fixed tothe side of the Rondel-type field cores 12 are also rotated, and theblades 14 a, 15 a revolve, whereby air flow takes place inside thegenerator. The air flows may be principally divided into: (1) flows (a)and (b) flowing in through an inlet port 3 a of the front bracket,passing through the coil end of the stator winding 22, and flowing outthrough an outlet port 3 b of the front bracket, and (2) flows (c) and(d) flowing in through an inlet port 4 a of the rear bracket, passingthrough the rectifier 5 and brush 6, and flowing out through an outletport 4 b of the rear bracket. The inside of the generator is cooled bythe air flows.

In the conventional battery charging alternating current generator ofthe above-mentioned construction and operation, a problem exists in thatthe space inside the battery charging alternating current generator islimited, making it impossible to enlarge the area of the blades 14 a, 15a of the fans 14, 15 and thus improve cooling efficiency, thus resultingin a temperature rise occurring inside the generator. In particular, thesurroundings of the stator 2 which generate heat during the powergeneration, are not sufficiently cooled.

Japanese Laid-Open Patent Publication (unexamined) No.194-65/1984discloses an alternating current generator in which a fan is bent to beclosely and securely fixed to a core. A problem, however, exists in thatsince the entire fan is bent along the core, a rather complicated shapeand assembly process are required. Moreover, the shape of the blades maybe disadvantageously deformed.

SUMMARY OF THE INVENTION

The object of the present invention is to solve the above-discussedproblems by providing an alternating current generator having improvedcooling efficiency, whose method of manufacture is easier.

Another object of the invention is to provide fans for use in analternating current generator which are easy to manufacture, can beeasily mounted on the alternating current generator, and are capable ofimproving the cooling efficiency of the alternating current generator.

An alternating current generator in accordance with the inventioncomprises: (1) a rotor having a rotary shaft and a field winding, whichis rotated by transmission of a driving force; (2) a bracket for holdingthe rotor rotatably; (3) a stator fixed to the bracket, having astationary core and a stationary winding; (4) fans fixed to the rotor;(5) blades formed directly from the fans in the direction toward thebracket; and (6) protruding portions formed directly from the blades inthe direction toward the rotor. Consequently, the fans, blades thereof,and protruding portions may be formed easily by press working, andcooling efficiency may be improved.

It is preferable that the blades and projecting portions of thealternating current generator are formed by cut-raising and that theprotruding portions are formed into a shape in line with the shape ofthe rotor. Consequently, a gap between the rotor and each protrudingportion may be reduced and the area of the protruding portions may beenlarged as much, resulting in improvement of cooling efficiency.

It is also preferable that the blades be formed by cut-raising the fanstoward the bracket side, with each blade being provided with a platefixed to an end of that blade and a projecting part being mounted on theend of each blade for the positioning of the plate. Consequently, theplates may be easily mounted, and the cooling efficiency may be improvedas a result of rectification effect and increase in area by theprojecting parts.

It is also preferable that the blades be formed by cut-raising the fanstoward the bracket and each blade is provided with a plate portionformed by bending an end portion of the blade. Consequently, the plateportions may be formed simultaneously at the time of press working ofthe fans, resulting in easy manufacturing.

Another embodiment of an alternating current generator in accordancewith the invention comprises: (1) a rotor having a rotary shaft and afield winding, which is rotated by transmission of a driving force; (2)a bracket for holding the rotor rotatably; (3) a stator fixed to thebracket, having a stationary core and a stationary winding; (4) fansfixed to the rotor; (5) blades formed rotatably on the fans; and (6)protruding portions formed on the blades into a shape that is in linewith the rotor. Consequently, a sufficient air flow rate is obtainedduring revolution at a low speed and a reduction of noise is achievedduring revolution at a high speed as a result of forming the rotatablefans. Furthermore, cooling performance may be improved as a result offorming the protruding portions.

It is also preferable that in the alternating current generator inaccordance with the invention the blades directed toward the bracket areformed by cut-raising, and that the protruding portions are formed inthe opposite direction of the bracket by simultaneously cut-raising themwhen cut-raising the blades directed to the bracket. Consequently, theinventive fans of improved cooling efficiency may be easily manufacturedby a press working operation.

The other objects and features of this invention will be understood fromthe following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a alternating current generator for acar in accordance with an embodiment of the present invention;

FIG. 2 is a perspective view showing a rotor in accordance with theembodiment shown in FIG. 1;

FIG. 3 is a partial perspective view showing a fan in accordance withthe embodiment shown in FIG. 1;

FIG. 4 is a perspective view showing a rotor in accordance with a secondembodiment of the present invention;

FIG. 5 is a partial perspective view showing a fan and a plate inaccordance with the embodiment shown in FIG. 4;

FIG. 6 is a perspective view showing a rotor in accordance with thethird embodiment 3 of the present invention;

FIG. 7 is a partial perspective view showing a fan and a plate inaccordance with the embodiment shown in FIG. 6;

FIG. 8 is a partial perspective view showing a fan and a plate inaccordance with the fourth embodiment of the present invention;

FIG. 9 is a partial plan view showing a fan and a plate in accordancewith a fifth embodiment of the present invention;

FIG. 10 is a partial sectional view showing a fan, a plate and a fieldcore during revolution at a low speed in accordance with the embodimentshown in FIG. 9;

FIG. 11 is a partial sectional view showing a fan, a plate and a fieldcore during revolution at a high speed in accordance with the embodimentshown in FIG. 9;

FIG. 12 is a partial sectional view showing a fan, a plate and a fieldcore during revolution at a low speed in accordance with a sixthembodiment of the present invention;

FIG. 13 is a partial sectional view showing a fan, a plate and a fieldcore during revolution at a high speed in accordance with the embodimentshown in FIG. 12;

FIG. 14 is a partial perspective view showing a fan in accordance with amodification of the foregoing embodiments of the present invention;

FIG. 15 is a sectional view showing a conventional alternating currentgenerator for a car;

FIG. 16 is a perspective view showing a rotor in the conventionalalternating current generator shown in FIG. 15; and

FIG. 17 is a partial perspective view showing a fan in the conventionalalternating current generator shown in FIG. 15.

In all figures, substantially same elements are given the same referencenumbers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a sectional view of an embodiment of an alternating currentgenerator for a car in accordance with the present invention. FIG. 2 isa perspective view of a rotor and, FIG. 3 is a partial perspective viewof a fan of the embodiment shown in FIG. 1.

The alternating current generator shown in FIG. 1 includes a rotor 100including a rotary shaft 110 driven by a driving force transmitted froman internal combustion engine of a car (not shown) through a belt (notshown), a pair of Rondel-type field cores 120, and a field winding 130.

A stator 200 having a stator core 210 and a stator winding 220, whichface the rotor 100, are spaced at a gap from the rotor 100.

A front bracket 300 and rear bracket 400 rotatably support the rotor 100through bearings 310, 410 and securely hold the stator 200 therebetween.

The Rondel-type field cores 120 are formed into a Rondel-type shape asshown in FIG. 2 by bend-raising nail portions 120 b projecting from acore portion 120 a, after forming a low carbon steel or the like into astar shape by forging. In such a forming step, since the nail portions120 b are raised by bending, an R portion (i.e., curved portion) isformed. It is also preferable to provide a taper on a shoulder portion120 c as shown in FIG. 2 in order to reduce turbulent air flow producedaround the Rondel-type field cores 120, that is to reduce wind noiseduring rotation of the rotor 100.

Fans 114, 115 are fixed to the Rondel-type field cores. Blades 114 a,115 a are formed by cut-raising the fans 114, 115. The number, area,shape, etc. of the blades 114 a, 115 a are restricted to a certainextent due to the desirability of a small sized apparatus, the magneticefficiency in the field cores, etc.

More specifically, the fans 114 and 115 are installed in the apparatus,together with the rotor 100, after being fixed to side surfaces of therotor 100, thus allowing them to rotate together with the rotor duringoperation. Therefore, the external diameter of the fans 114 and 115 arerestricted by the internal diameter of the stator 200, while theinternal diameter of the fans 114, 115 are restricted by the externaldiameter of bearing holders, etc. of the brackets 300, 400.

Furthermore, the height of each of the blades 114 a, 115 a formed bycut-raising the fans 114, 115 is restricted to a height that preventscontact with other incorporated members of the assembly.

The fans 114, 115 are respectively provided with ten blades 114 a, 115 aformed by cut-raising the fans toward the brackets 300, 400. Of course,any suitable number of blades could be provided. The blades 114 a, 115 aare provided with substantially triangular protruding portions 114 b,115 b formed in the direction of the field core 120 of the rotor 100.

The protruding portions 114 b, 115 b are formed by cut-raising in theopposite direction of the blades 114 a, 115 a (i.e., in the direction ofthe Rondel-type field core 120) at the same time as the blades 114 a,115 a are cut-raised.

The blades 114 a, 115 a may be formed Perpendicular or almostperpendicular to the axis of the rotor, because cooling air will beproduced as long as they are not formed horizontally. However,considering the effective cooling area, the more perpendicular theblades are formed, the higher the cooling efficiency that is achieved.Thus, the blades 114 a, 115 a, including the protruding portions 114 b,115 b, generate a cooling air flow during rotation of the rotor 100.

The protruding portions 114 b, 115 b are formed into a shape in line orsubstantially in line with the shoulder portion 120 c of the Rondel-typefield core 120. Accordingly, since the shoulder portion 120 c is taperedto be substantially triangular in this embodiment, the protrudingportions 114 b, 115 b are also formed triangular or substantiallytriangular.

As a result of the forming of protruding portions 114 b, 115 b, it maybe said that effective area of the blades 114 a, 115 a of the fans 114,115 becomes larger or increased by the area of the protruding portions114 b, 115 b, resulting in improvement in cooling performance of thefans 114, 115. Furthermore, as the protruding portions 114 b, 115 bextending inward from the fans 114, 115 may increase air flow senttoward the stator core 210 and the stator winding 220, cooling of thestator core 210 and the stator winding 220, which both generate heatduring the power generating operation, is greatly improved.

In such a cooling operation, the area of the blades 114 a, 115 a of thefans 114, 115 represent the effective cooling area, such that a largereffective area causes greater air flow rate. It is to be noted in thisembodiment that since the blades 114 a, 115 a are formed almostperpendicular to the fans 114, 115, there is no large difference betweenthe actual area of the blades 114 a, 115 a and their effective area.

The fans 114, 115 are formed from a metal plate sheet by the action of apress, wherein notches for forming the blades 114 a, 115 a are alsoformed at the time of press working. At the time of cut-raising theblades 114 a, 115 a, the protruding portions 114 b, 115 b aresimultaneously cut-raised.

Accordingly, by varying the cutting line for the cut-raising operation,the shape of the protruding portions 114 b, 115 b may be changed. Thus,even if shape of the shoulder portion 120 c of the Rondel-type fieldcores 120 is complicated, the shape of the protruding portions 114 b,115 b may be easily adjusted.

This situation is the same for blades 114 a and 115 a. That is, theshape of the blades 114 a, 115 a may be easily varied in conformancewith the internal shape of the brackets 300, 400.

With regard to the operation of the alternating current generator of theabove construction, when the rotor 100 is rotated by an external drivingforce, a magnetic field generated by the field winding 130 surrounds theRondel-type field cores 120, and the magnetic field passes through thestator winding 220 in conformance with the rotation of the rotor 100. Inthis manner, a current is generated in the stator winding 220 and poweris generated through a rectifier 500.

Furthermore, when the rotor 100 is rotated, the fans 114, 115 fixed tothe side of the Rondel-type field cores 120 are rotated together, andthe blades 114 a, 115 a and the protruding portions 114 b, 115 b, bothcut-raised from the fans 114, 115, are also rotated to produce air flowinside the generator.

The air flows may be principally divided into flows (A) and (B) or flows(C) and (D). Flows (A) and (B) represent air flowing in through an inletport 300 a of the front bracket, passing through the coil end of thestator winding 220, and flowing out through an outlet port 310 b of thefront bracket.

Flows (C) and (D) represent air flowing in through an inlet port 400 aof the rear bracket, passing through the rectifier 500 and brush 600,and flowing out through an outlet port 400 b of the rear bracket. Theinside of the generator is cooled by these air flows.

In the first embodiment, since the fans may be formed by only one pressworking step as described above, productivity is improved and costreduction is achieved.

Furthermore, since the gap between the shoulder portion 120 c and theblade 114 a or 115 a of the Rondel-type field cores 120 may be small,even if the blades 114 a, 115 a are deformed toward the externaldiameter of the rotary shaft 110 during revolution of the rotor 100, thedeformation of the blades 114 a, 115 a may be minimized by theprotruding portions 114 b, 115 b contacting the shoulder portion 120 c.

A second embodiment of the invention relates to a mounting structure ofthe plates.

FIG. 4 is a perspective view showing the second embodiment, while FIG. 5is a partial perspective view showing a plate and a fan in the sameembodiment. In the figures, like reference numerals designate the sameparts as those found in the foregoing first embodiment, so that furtherdescription thereof is omitted below.

Annular metal plates 216, 217 are fixed to ends of the blades 114 a, 115a, respectively, on the bracket sides by adhesion or welding.

The plates 216, 217 are formed into a shape capable of rectifyingcooling air produced during revolution, together with the fans 114, 115.More specifically, passage of a cooling air flow is divided by theplates 216, 217, whereby turbulent air flow is diminished, thus inimprovement in cooling efficiency and reduction in noise.

The passage of air flow divided by the plates 216, 217 and the blades114 a, 115 a is directed to the stator 200, whereby the efficiency ofcooling the stator core 210 and the stator winding 220 is improved as aresult of mounting of the plates 216, 217.

Furthermore, as a result of mounting of the plates 216, 217, the blades114 a, 115 a are fixed by both the Rondel-type field cores 120 and theplates 216, 217, which improves the structural strength of the blades,preventing the blades from being distorted during revolution, whicheventually results in improvement in apparatus reliability.

In addition, the plate 216 shown in FIG. 5 is provided with a projection216 a at its center, this projection serving as a welded part forcarrying out projection welding of the plate 216 to the blade 114, whichis a type of resistance welding. Plate 217 has a similar projection.

The third embodiment of the invention relates to a positioning structureof the plates.

FIG. 6 is a perspective view showing the third embodiment, and FIG. 7 isa partial perspective view showing the blade 314 a and the plate 216. Inthe figures, like reference numerals designate the same parts as thosefound in the foregoing embodiments, so that further description thereofis omitted below.

Reference numerals 314, 315 designate fans formed by press working whichare fixed to the Rondel-type field cores 120.

The fans 314, 315 are respectively provided with ten blades 314 a, 315 aformed by cut-raising. Any suitable number of blades, however, could beprovided. The blades 314 a, 315 a are respectively provided withtriangular or almost triangular protruding portions 314 b, 315 b formedat the time of the cut-raising in the direction of the Rondel-type fieldcores 120.

The protruding portions 314 b, 315 b are formed into a shape in line orsubstantially in line with the shape of the shoulder portion 120 c ofRondel-type field cores 120.

Rectangular projecting portions 314 c, 315 c projecting along the plates216, 217 are respectively formed on the sides of the blades 314 a, 315 ato be in line with the shape of the plates 216, 217. The projectingportions 314 c, 315 c are useful for positioning at the time of fixingthe plates 216, 217 to the fans 314 and 315, respectively.

The projecting portions 314 c, 315 c also contribute to an increase theeffective area of the blade 314 a resulting in increase in air flowrate.

A fourth embodiment of the invention also relates to a positioningstructure of the plates.

FIG. 8 is a partial perspective view showing the blade 314 a and theplate 216 according to the fourth embodiment. In this figure, likereference numerals designate the same parts as those found in theforegoing embodiments, so that further description thereof is omittedbelow.

Reference numeral 314 d designates a projecting portion formed on theplate side of the blade 314 a. The plate 216 is positioned between theprojecting portion 314 c and the projecting portion 314 d at itsinternal and external diameter sides, respectively, resulting in moreexact positioning.

The projecting portions 314 c, 314 d also contribute to increase theeffective area of the blade 314 a, resulting in an increase of the airflow rate.

In the foregoing third and fourth embodiments, the positioning of theplates 216, 217 may be made easier by forming a part of the projectingpotion 314 c or the projecting portion 314 d into a “]” shape.Furthermore, fixing of the plates 216, 217 also becomes more exact. Theprojecting portions 314 c, 314 d are disposed so as not to contact thebracket, etc. during rotation of the rotor 100.

Although the plates 216, 217 are metal plates in the foregoing secondthrough fourth embodiments, plates of any other material such as resinare also satisfactory.

Although the plates 216, 217 are annular metal plates in the foregoingsecond through fourth embodiments, plates of any other shape such as adisk shape provided with a plurality of holes are also satisfactory.

Although the plates 216, 217 are separate members from the fans 114,115, it is also possible that, as shown in FIG. 14, the ends of theblade portions of the fans 114, 115 are further bent to form a plateportion 115 p, whereby substantially the same rectification effect asthat of the separate plate may be accomplished, resulting insubstantially the same cooling effect.

In the foregoing first through fourth embodiments, it is also possibleto fix the protruding portions 114 b, 115 b to the shoulder portion 120c.

Although the fans are formed of metal plates in the foregoingembodiments, fans may also be formed of any other material such as resin(by a molding process). In such a modification, the blade portions maybe formed simultaneously at the time of molding.

Although the fans 114, 115 are formed from a sheet of metal plate by apress working operation in the foregoing embodiments it is also possibleto separate them into plural parts that are separately formed and fixedto the field cores 120.

The fifth embodiment of the present invention relates to a rotatableblade structure.

FIG. 9 is a partial plan view showing the fifth embodiment. FIG. 10 is asectional view showing a state before the revolution of moving blade416. FIG. 11 is a sectional view showing a state after the revolution ofthe moving blade 416. In the figures, like reference numerals designatethe same parts as those found in the foregoing embodiments, so thatfurther description thereof is omitted below.

A main plate 414 of a fan is fixed to the Rondel-type field core. Amoving blade 416 of resin or the like is formed separately from the mainplate 414. A plate 417 is similar to the plates 216, 217 shown in thesecond embodiment. A support 418 is vertically erected, whose ends arefixed to the main plate 414 and to the plate 417, serving as a centershaft during revolution of the moving blade 416.

A coil spring 419 is stored in the blade 416 whose end is fixed to theblade 416 and whose other end is fixed to a spring stopper of the mainplate 414. The blade 416 is held at its position by an urging force ofthe coil spring so long as the rotor is rotated at a low speed.

If the rotor is rotated at a high speed, the blade 416 is caused to turnaround the support 418, due to an angular moment produced by acentrifugal force which becomes larger than the urging force of a coilspring 419, causing contact with the stopper 414 b of the main plate414, whereby the turning of the blade 416 is stopped and held at thatposition.

As shown in FIGS. 10 and 11, the blade 416 is enlarged toward the upperface of the plate 417 (i.e., an enlarged part 416 b serving as aprojecting portion in FIGS. 10 and 11) and also to the field core side(i.e., an enlarged part 416 a serving as a protruding portion in FIGS.10 and 11).

The operation of the moving blade is described below.

Generally, the output of the alternating current generator is saturatedat a predetermined rpm, while a cooling air flow rate produced by acooling fan is increased in proportion to the rpm, while the wind noiseis also increased.

In this regard, the temperature rise value of every part inside thegenerator cooled by the cooling fan is dependent upon a relation betweenthe output and air flow rate. For example, in a generator whoserevolving speed at saturation output is 5000 rpm or so, the maximumpoint is in the range of 2000 to 3000 rpm, and the temperature risevalue is sufficiently small due to sufficient cooling air flow rateduring revolution at a high speed not lower than approximately 5000 rpm.

To reduce wind noise, which is a problem during revolution at a highspeed, the moving blades are turned to restrain the air flow rate,whereby not only the temperature rise value is kept within an allowablelevel in every part but also the wind noise may be reduced.

It is to be noted that there is no variation in the air flow rate of thefans provided with the fixed blades as shown in the foregoing firstembodiment, but that in the fans provided with moving blades as shown inthe fifth embodiment, the moving blade 416 turns around the support 418due to the centrifugal force acting on the center of gravity duringrevolution at a high speed, whereby the blade angle and externaldiameter of the moving blade vary, resulting in securing an appropriateand sufficient air flow rate.

Accordingly, when a sufficient cooling air flow rate is secured forrevolution at a low speed or when the cooling air flow rate isexcessively large for revolution at a high speed, the air flow rate maybe restrained to reduce wind noise.

In addition, in the fifth embodiment, the blade 416 is formed to beenlarged, in order to be in line or almost in line with the side surfaceof the field cores during revolution at a high speed and to prevent theenlarged part 416 a of the blade 416 from contacting the shoulder partof the field cores. Consequently, the blade area is increased resultingin improvement in cooling efficiency, particularly during revolution ata low speed when a larger air flow rate is required.

A sixth embodiment relates to a rotatable blade structure.

FIGS. 12 and 13 are sectional views both showing the sixth embodiment,where FIG. 12 shows revolution at a low speed and FIG. 13 showsrevolution at a high speed. In the figures, like reference numeralsdesignate the same parts as those found in the foregoing embodiments, sothat further description thereof is omitted below.

Reference numeral 516 a designates an enlarged portion, which isenlarged from the moving blade 416 to the field core 120 side. Theenlarged portion 516 is formed into a shape in line or substantially inline with the shape of the shoulder portion 120 c of the field cores120, and in this embodiment, the enlarged portion 516 comes closest tothe shoulder portion 120 c during revolution at a high speed as shown inFIG. 13, whereby a gap formed in line with the shape of the shoulderportion 120 c between the enlarged portion 516 and the shoulder portion120 c is minimized. On the other hand, during revolution at a low speedshown in FIG. 12, the enlarged portion 516 is separate from the shoulderportion 120 c, and a larger gap is formed therebetween.

Although the stopper 414 b is formed on the main plate of the fan in theforegoing fifth and sixth embodiments, it is also preferable that theenlarged portions 416 a, 516 a of the moving blade 416 come in contactwith the shoulder portion 120 c of the field core instead of forming thestopper.

Although the projecting portions of the blade formed into a shape inline or substantially in line with the shoulder portion of theRondel-type field core are shown in the foregoing embodiments, it isalso preferable to form the projecting portions along the stator or thefront and rear brackets.

Although the invention is described with respect to the alternatingcurrent generator for a car provided with Rondel-type field cores, anyother alternating current generator is as the generator is provided witha rotor. For example, the fans are applicable to an alternating currentgenerator for a car provided with star-shaped field cores.

Although the invention is described with respect to the alternatingcurrent generator for a car in the foregoing embodiments, it is alsopossible to apply the invention to any other alternating currentgenerators. However, considering the requirements of installation in aquite limited space or the need of a certain cooling performance under ahigh temperature, the invention is particularly advantageous in analternating current generator for a car or any other alternating currentgenerator put in use under similar conditions.

While the presently preferred embodiments of the present invention havebeen shown and described, it is to be understood that these disclosuresare for the purpose of illustration and that various changes andmodifications may be made without departing from the scope of theinvention as set forth in the appended claims.

What is claimed is:
 1. An alternating current generator comprising: arotor having a rotary shaft and a field winding which rotates bytransmission of a driving force applied thereto; a bracket for rotatablysupporting said rotor; a stator fixed to said bracket and having astationary core and a stationary winding; a fan, fixed to said rotor,having a plurality of blades extending towards said bracket and aprotrusion formed on each of said blades extending towards said rotor;and one or more plates respectively fixed to ends of said blades onsides of said blades nearest said bracket for rectifying cooling airproduced during revolution of said fan; and wherein said plurality ofblades and said plurality of protrusions are press-formed portions ofsaid fan; and wherein said blades further comprise projection portionsextending towards said bracket at an inner circumference of said one ormore plates configured to accurately position said one or more plates onsaid respective blades, and so as to support said one or more plates inan axial direction.
 2. The alternating current generator according toclaim 1, wherein said one or more plates are respectively fixed to endsof said blades by welding.
 3. An alternating current generatorcomprising: a rotor having a rotary shaft and a field winding whichrotates by transmission of a driving force applied thereto; a bracketfor rotatably supporting said rotor; a stator fixed to said bracket andhaving a stationary core and a stationary winding; a fan, fixed to saidrotor, having a plurality of blades extending towards said bracket and aprotrusion formed on each of said blades extending towards said rotor;and one or more plates respectively fixed to ends of said blades onsides of said blades nearest said bracket for rectifying cooling airproduced during revolution of said fan; and wherein said plurality ofblades and said plurality of protrusions are press-formed portions ofsaid fan; and wherein said blades further comprise projection portionsextending towards said bracket both at an inner circumference of saidone or more plates and at an outer circumference of said one or moreplates configured to accurately position said one or more plates on saidrespective blades, and so as to support said one or more plates in anaxial direction.
 4. The alternating current generator according to claim3, wherein one or more plates are respectively fixed to ends of saidblades by welding.